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Acoustotaxis - In vitro stimulation in a wound healing assay employing surface acoustic waves

M. E. M. Stamp, M. Brugger, A. Wixforth, C. Westerhausen

Biomater. Sci. (2016) DOI: ACS Nano


Piezoelectric surface acoustic waves are employed to induce radio frequency spatio-temporal dynamics of photogenerated electrons and holes in the GaAs core of individual GaAs/AlGaAs core/shell semiconductor nanowires. Comparison of the time-dependent interband optical recombination to numerical simulations allow to determine the charge carrier transport mobilities of electrons, µe=500cm2/Vs, holes, µh=50cm2/Vs and their ratio µeh=20:1.Our method probes carrier transport at low carrier density. Thus, the obtained values represent the native material limit of these nanowires, determined by their structural properties. We show that for near-pristine nanowires, individual twin defects do not significantly affect electrical transport, in strong contrast to polytypic nanowires. In the acousto-electrically modulated emission we observe unambiguous signatures of (i) hole localization within long wurtzite-rich segments and (ii) electrons in zinc blende regions being reflected at the interface to a wurtzite-rich region. The experimentally observed periodic emission bursts are faithfully reproduced by advanced numerical simulations which include static band edge discontinuities between a single wurtzite segment in an otherwise pure zinc blende nanowire. Otherwise using the same input parameters as for near-pristine zinc blende nanowires we can deduce from our simulations a minimum conduction band offset of ΔEC≈ 20 meV at the interface between the zinc blende part and the wurtzite-rich region. These results furthermore confirm that a single wurtzite segment with sufficiently large band offsets efficiently traps holes and blocks electron transport.